1. Field of the Invention
This invention concerns a compound inductive/MR type thin film magnetic head, provided integrally with an inductive head for writing and a magnetoresistive (MR) head for reading, and used for example in hard disk devices and in other recording and playback devices of various electronic equipment such as computers and word processors.
2. Background Information
In recent years, thin film magnetic heads employing magnetic materials with high saturation flux densities have been widely adopted in order to increase capacities and raise densities in magnetic recording. In particular, recently efforts have been made to further raise recording densities, reduce device sizes and raise output by means of compound type thin film magnetic heads, which adopt for dedicated writing an inductive head frequently used in the past for both reading and writing, and integrate with this an MR head for dedicated reading which has a high reproduction sensitivity and the reproduction output of which is independent of the relative velocity of the recording media.
In early compound thin film magnetic heads, the lower magnetic film of the inductive head for writing and the upper shield of the MR head for reading were separated magnetically from each other by a relatively thick nonmagnetic insulating layer, as described in examined patent application Sho58-36406. In general, thin film magnetic heads are provided in a slider supported at the tip of a suspension arm, and are used in a state of flight in proximity to the surface of a rotating magnetic disc. Here changes occur in the skew angle at outer circumferences and inner circumferences of the rotating magnetic disc; in order to alleviate this difficulty, it is desirable that the write gap and the read gap be brought into as close proximity as possible. Hence it was proposed that a compound type head be used, with a structure in which the upper shield of the MR head also serves as the lower magnetic film of the inductive head, as described for instance in laid-open patent application Hei7-296331.
However, there is the problem that in this structure the width of the lower pole of the inductive head is extremely large compared with the upper pole width, so that considerably large side fringes occur during recording, and limits are placed on the reduction of the track width. Hence in laid-open patent applications Hei7-262519 and Hei10-143817 and elsewhere, a structure is adopted in which the upper pole of the inductive head and the rectangular-shape protrusion below the magnetic gap film, that is, the lower pole part, are formed with their side walls positioned in vertical alignment to have the same track width, so that while maintaining the function as the upper shield of the MR element, side fringes are minimized, and off-track characteristics are improved.
In general, an upper shield having a lower pole part consisting of such a rectangular protrusion can be formed such that the track width of the upper pole, magnetic gap film and lower pole part are equal, by using ion milling to partially remove the magnetic film on both sides using the upper pole as a mask, or by using a frame plating method for formation in layers of the lower pole part on top of the magnetic film to function as the upper shield of the MR head. Normally ion milling is performed in two stages, first at a certain angle with respect to the side walls of the upper pole, and preferably at an irradiation angle close to the perpendicular, as described in both the aforementioned patent publications, after which the irradiation angle is changed to a more oblique direction.
By thus performing ion milling with the ion irradiation angle changed in two stages, the aforementioned protrusion which becomes the lower pole part can be made more nearly rectangular, and its side walls can be aligned with the side walls of the upper pole, while at the same time magnetic film material which has again adhered to the side walls of the upper pole, the magnetic gap film and the lower pole part can be removed. Further, in laid-open patent application Hei10-143817, by means of a second ion milling in which the irradiation angle is made more oblique inclined faces are formed on the upper faces on both sides of the protrusion; this part is more distant from the upper pole than in the prior art, so that there is the advantage that side fringes are not formed as easily.
In addition, in laid-open patent application Hei8-129720 is described a compound type thin film magnetic head in which the lower core layer of the inductive head and the upper shield layer of the MR head are formed integrally or else formed integrally with an intervening nonmagnetic thin film, in order to alleviate the problem in which, as the track width is made more narrow, closure domains grow larger in the magnetic core layer of the inductive head near the face opposing the recording media, reducing the recording performance. In the upper shield layer/lower core layer, the convex part corresponding to the lower core layer with planar shape approximately the same as the upper core layer of the inductive head, and the base part corresponding to the upper shield layer of the MR head with a wider planar shape, are magnetostatically coupled, and by this means the occurrence of closure domains in the vicinity of the surface opposing the recording media is suppressed, the effective permeability is raised, and recording performance can be improved. The convex part of the upper shield layer is formed into a flat shape approximately equal to the upper core layer by means of etching of the magnetic thin film according to a resist pattern formed on top of the latter.
However, in the upper shield of the compound magnetic head of the prior art described above, there is the problem that the part functioning as the lower pole of the inductive head for writing and the part functioning as the upper shield of the MR head are not clearly separated, so that the write magnetic field generated between the upper and lower poles of the inductive head cannot be adequately shielded, and the magnetization state of the MR film easily becomes unstable. In particular, it is undesirable for the domains to change from the position at which the planar shape of the upper shield changes, such as for example between the protrusion of the lower pole part and the part below this, or the inclined-face parts on both sides of the protrusion and the part below this. Otherwise there is the concern that noise and waveform distortion may occur in the reproduction signal, reducing the reproduction performance of the MR head and detracting from reliability.
A compound thin film magnetic head is disclosed. In one embodiment, the compound thin film magnetic head includes a substrate and an inductive head on the substrate for writing. The inductive head includes a conducting coil and an insulating layer formed in layers between an upper magnetic film and a lower magnetic film. The compound thin film magnetic head further includes a magnetoresistive head for reading. The magnetoresistive head includes a magnetoresistive element enclosed between the lower magnetic film serving as an upper shield and a lower shield. A lower power pole part is included in the upper shield, having a protrusion on a side of the inductive head opposing an upper pole of an upper magnetic film tip with a magnetic gap layer in between. An upper shield part is included on a side of the magnetoresistive head that is wider than the lower pole part. A nonmagnetic separation film is provided at a position of the upper shield part at which a planar shape of the upper shield part changes.